The field of the present disclosure relates generally to systems and methods for item checkout and in certain aspects to retail or other checkout stands (e.g., a parcel distribution station) that incorporate data readers and other electronic devices. The field of the present disclosure further relates to systems and methods for determining the position and movement of multiple items on a conveying system using radio frequency identification (RFID) tags on the items.
Radio frequency identification is the wireless use of electromagnetic fields to transfer data, primarily for the purposes of automatically identifying and tracking tags attached to various objects. The tags contain identifier codes and other electronically stored information that is accessible and readable by an RFID reader. RFID technology is used in a wide variety of fields, such as, for example, in the retail industry for tracking packages and goods during an automated checkout process or in inventory, the medical industry to track medicines and pharmaceuticals, and the manufacturing industry to track progress of parts through assembly lines.
In the retail industry, items may be identified, tracked, and decoded using a variety of systems and methods. For example, items may have RFID tags and/or optical codes (such as barcodes), and various types of systems may be used to transport the items toward a data reading device to capture the target data. In a semi-automatic system, either checker-assisted or self-checkout, objects bearing RFID tags and/or optical codes are moved one at a time by the user into or through the read region of the data reading device, at which the device captures the data from the object. In an automated system (e.g., a tunnel or portal scanner), an object is automatically moved via a transportation or conveying system through the read region, at which the reader automatically captures data from the object when the object passes through the read region.
The present inventors have identified certain disadvantages with conventional checkout systems that use RFID technology to identify and track objects. For example, many checkout systems assume that the conveyor belt speed and trajectory of the RFID-tagged objects are known and constant parameters. On the contrary, the present inventors have identified that these parameters are typically variable in real-life scenarios since the conveyor belt speed may change for any number of reasons and the relative position of the RFID tags may be different from item to item due to the size, shape, and/or placement of the tagged items on the conveyor belt.
In addition, many methods developed for identifying RFID location present several drawbacks. For example, some RFID locating methods rely on very directive antenna and/or antenna arrays, which significantly increases the cost and complexity of the system. As another example, some RFID location processes are based on the intensity of the received signal (RSSI), which indicates the strength of the signal sent from an RFID tag to an RFID reader. RSSI is typically used for estimating the distance between the RFID tag and RFID reader (a stronger signal indicates an item closer to the RFID reader), and identifying movement direction of the item bearing the RFID tag based on the strength of the signal. However, using RSSI alone tends to result in imprecise and inaccurate readings because environmental variables largely affect the strength of the signal from the RFID tag. This issue may be especially problematic in a retail setting because many of the retail items themselves affect RSSI data. For example, items with metallic or other reflecting materials (such as soda cans, canned foods, etc.) may cause signals to bounce uncontrollably, thereby weakening the signal and making the RFID tagged item appear further away from the RFID reader. In addition, liquids (such as milk, water, etc.) may absorb a portion of the signal, or larger items may obstruct the signal from smaller items, thereby causing the signal to appear weaker and resulting in an inaccurate estimation of an item's location.
The present inventors have, therefore, determined that it would be desirable to have a simple and streamlined system with improved performance features for accurately locating RFID tags while taking into account the variable speed of the conveyor system and the changing trajectory of the tagged items. Additional aspects and advantages of such data reading systems will be apparent from the following detailed description of example embodiments, which proceed with reference to the accompanying drawings.
Understanding that the drawings depict only certain embodiments and are not, therefore, to be considered limiting in nature, these embodiments will be described and explained with additional specificity and detail with reference to the drawings.